It has long been the practice in urban areas to distribute electrical power via sub-surface or subterranean high-voltage power cables. However, once these cables reach the ends of their operational lifetimes, or are otherwise de-commissioned, the cables are usually left in the ground by the utility companies. The reasons for this are generally due to the expense of excavating the cables and also to the potential disruption and delay caused to traffic in urban areas (e.g. city centres etc.). Since the cables typically run for hundreds of metres underground, the problem of removal is significant, as excavating channels of this length through urban areas, even if broken into shorter sections, is not generally practical and in any event is considerably time consuming.
Moreover, in addition to the potential expense and disruption, there are also environmental concerns relating to the removal of decommissioned cables. Virtually all high-voltage power cables contain a copper core as the electrical conductor. However, many of the older cables also contain an inner sheathing comprising an oil impregnated paper that is wrapped around the copper core, on top of which may be a layer of lead as well. The oil and paper serve as an insulator to the current carrying core, which is then enclosed by an outer sheathing, typically a thick rubber or plastic coating. Therefore, the oil and paper sheathing presents a significant hazard to the immediate environment in the vicinity of the cables, as any leakage of the oil (arising from the removal of the cables) can seep into the ground and may contaminate the local environment, while also possibly causing problems with nearby drainage and sewerage flow etc. Hence, it is certainly desirable to avoid any of the oil entering the environment.